Abstract:
Macrophomina root rot disease (MRRD) caused by Macrophomina phaseolina is an emerging threat to the profitable cowpea production in northern Ghana.
Recommended control methods including the use of fungicides are ineffective and expensive for resource poor
farmers whilst biocontrol options are not commercially available. An integrated method based on host plant
resistance is considered the cheapest and most effective method of managing the disease. This study sought to
confirm and characterize previously identified MRRD isolates from Northern Ghana using molecular technology,
and to identify cowpea with potential sources of resistance to the MRRD. A PCR assay of ten isolates of the cowpea
root rot pathogen revealed all isolates belonged to the species M. phaseolina, whilst a nucleotide BLAST of eight
isolates showed 98% similarity with the sequences of Macrophomina isolates from other host available in GenBank. A sick pot method evaluation of 49 cowpea lines found 10 lines resistant to MRRD on a 1–9 disease severity
scale (disease score, less than 5). A selection of eight resistant lines (Suvita 2, Abagbaala, IT97K573-1-1, IT93K 503-1-1, Hewale, AV2 3224, Nhyira and T2T4), and a susceptible check (Songotra) were evaluated against 10
isolates of M. phaseolina using a sick pot method. All the genotypes except for the susceptible check were resistant
to MRRD. Thus, these genotypes could be used in cowpea MRRD resistance breeding programs.
